Mounting adapter for air-assist fuel injector

Abstract: An adapter (18) for mounting an air-assisted fuel injector (10) on an engine is a one-piece molded plastic part that includes an integral assist-air supply tube (32) through which assist air enters the adapter and integral attaching catches (34,36,38,40).

Description: Field of the Invention This invention relates to fuel-injectors for internal combustion engines, particularly fuel injectors having air-assist nozzles for enhancing atomization of fuel as it is being injected. Background and Summary of the Invention In some engines requiring air-assisted fuel injectors, the injectors are mounted in an air-assist manifold that serves all injectors. In other engines, assist air may be fed to each injector through its own tube. In both, there is a need for adaptation to the engine so that leakage is avoided. A number of patents disclose various forms of individual adapters for individually mounting an air-assist type fuel injector on an engine. For example, please refer to U.S. patent No. 5,218,943. One known adapter comprises a metal receptacle for receiving the nozzle end of a fuel injector and a metal tube that is joined by a process such as brazing, welding, etc. to a hole in the sidewall of the receptacle for communicating assist air to an axially sealed zone inside the receptacle surrounding assist air entrances of the air-assist nozzle. Another known form of adapter is disclosed in German patent application DE 42 05 709. The air-assist adapter comprises a one-piece body which enshrouds a nozzle. A single air-assist orifice is located directly beneath the nozzle. An air-assist tube is provided in a wall of the adapter for conveying air from an external source. The adapter is provided with catch means for securing the adapter to the fuel injector. While the use of metal parts in an adapter may be acceptable, care must be taken during the fabrication process to guard against the creation of sharp edges, burrs, weld spatter, etc., which may have the potential for damaging seals that are necessary in order to provide proper sealing of the injector to the adapter to the engine. Likewise, care must be exercised to assure compliance with the typically tight tolerances that are involved in fitting to an injector and to an engine. Naturally, these measures may be reasonably anticipated to add the cost of the adapter and its installation. Avoidance of these measures is apt to make an air-assist fuel injection system more competitive. Development of a fuel injection system for an engine may involve substitution of parts in order to arrive at the best possible combination. The ability to quickly and conveniently make substitutions of fuel injector system components should contribute to a decrease in the development time and should enhance the ability to substitute fuel injector system components at any time, such as after the engine has gone into service. Briefly, the invention involves the creation of an adapter for adapting an air-assist nozzle of a fuel injector to an engine by using a molding process like injection molding to create a one-piece molded plastic adapter. The resultant adapter possesses certain structural features not found in earlier adapters. One important feature is the snap-on, snap-off attachment of the adapter to an air-assist fuel injector. This feature is provided by integrally formed catches. The user of plastic injection molding also offers the potential for avoiding sharp edges, burrs, etc. Because the adapter is one-piece, it does not have to be fabricated by joining several individual components together. The foregoing features, advantages, and benefits of the invention along with additional ones will be seen in the ensuing description and claims which are accompanied by a drawing that shows a presently preferred embodiment of the invention according to the best mode presently contemplated for carrying out the invention. According to the present invention, there is provided an adapter for an air-assist fuel injector which comprises a nozzle including a plurality of air-assist entrances for receiving assist air into the fuel injector for mixing with fuel therein, the adapter comprising :- a tubular body having main wall means circumferentially girdling a main through-bore in which a portion of the injector including the air-assist entrances is mounted; resilient catch means for securing the tubular body to the fuel injector, the catch means providing a snap-on, snap-off attachment with the fuel injector; axially spaced apart seals acting between the main wall means and the fuel injector to define an annular zone around the air-assist entrances; and tube means connected to the wall means and in fluid communication with the annular zone to convey assist air from an external source thereto; characterised in that the resilient catch means comprises a plurality of fingers which project from the wall means, the fingers being circumferentially distributed about the body, and in that the tubular body further comprises a plurality of wall sections circumferentially distributed thereabout which join with and extend axially of the main wall means, the wall sections being circumferentially interdigitated with the fingers and extend further from the main wall means than the fingers. Brief Description of the Drawing FIGURE 1 is a longitudinal view of an air-assist fuel injector and includes in cross-section an adapter in accordance with principles of the invention. FIGURE 2 is a top plan view of the adapter by itself. FIGURE 3 is a cross-sectional view in the direction of arrows 3-3 in Figure 2. Description of the Preferred Embodiment Fig. 1 shows a top-feed fuel injector 10 comprising an inlet tube 12 via which pressurized fuel enters and an air-assist nozzle 14 from which fuel is injected. Nozzle 14 comprises several entrances 16 via which assist air enters nozzle 14. An adapter 18 is assembled onto fuel injector 12, fitting over nozzle 14, as shown in Fig. 1. Adapter 18 comprises a one-piece body 20 of fuel-compatible plastic that has a circular wall 22 circumferentially girdling a through-bore 24 that receives the nozzle end of the fuel injector. Axially spaced apart O-ring seals 26, 28 disposed around the outside of the fuel injector seal between the outside of the nozzle sidewall and the inside of wall 22 to axially bound and seal an annular zone 30 that is radially inwardly bounded by the outside of the nozzle and radially outwardly bounded by the inside of wall 22. Entrances 16 are open to this zone 30. Assist air is delivered to zone 30 through a tube 32 that transversely intersects wall 22 for conveying assist air from an external source through wall 22 to zone 30 from whence it can pass into entrances 16 to act on the injected fuel. Attachment of adapter 18 to fuel injector 10 is provided by two fingers 34, 36 diametrically opposite each other that join with and project axially from wall 22 toward the fuel injector inlet. The distal ends of fingers 34, 36 contain catches 38, 40 on their radially inner faces that catch in a circumferential groove 42 extending around fuel injector 10. Body 20 further has two additional wall sections 44, 46 that join with and extend axially from wall 22. Wall sections 44, 46 are circularly curved in shape and are interdigitated with fingers 34, 36. The fingers 34, 36 and the wall sections 44, 46 circumferentially girdle an entrance portion of through-bore 24 via which the adapter is assembled onto and disassembled from the fuel injector, although sections 44, 46 extend slightly beyond the distal ends of the fingers. Catches 38, 40 have tapered surfaces that engage the outside of the fuel injector body as the adapter is being assembled onto the fuel injector to facilitate the assembled. Fingers 34, 36 are cantilever-mounted to flex slightly during assembly, until catches 38, 40 come to groove 42, at which point the flexed fingers relax to lodge the catches in the groove. Adapter 18 is fabricated by injection molding a suitable plastic that can withstand the fuels and temperatures encountered in use. The parts of the adapter that have been illustrated and described are integrally formed during the molding process that creates the one-piece part. This is a significant improvement over prior adapters. The adapter can be conveniently installed, and conveniently removed when necessary. For best sealing in installed position, the outside of the adapter has an O-ring seal 48 around it proximate the end through which the injected fuel passes.

Claims: An adapter (18) for an air-assist fuel injector (10) which comprises a nozzle (14) including a plurality of air-assist entrances (16) for receiving assist air into the fuel injector (10) for mixing with fuel therein, the adapter (18) comprising :- a tubular body (20) having main wall means (22) circumferentially girdling a main through-bore (24) in which a portion of the injector (10) including the air-assist entrances (16) is mounted; resilient catch means (34, 36, 38, 40) for securing the tubular body (20) to the fuel injector (10), the catch means (34, 36, 38, 40) providing a snap-on, snap-off attachment with the fuel injector (10); axially spaced apart seals (26, 28) acting between the main wall means (22) and the fuel injector (10) to define an annular zone (30) around the air-assist entrances (16); and tube means (32) connected to the wall means (22) and in fluid communication with the annular zone (30) to convey assist air from an external source thereto; characterised in that the resilient catch means (34, 36, 38, 40) comprises a plurality of fingers (34, 36) which project from the wall means (22), the fingers (34, 36) being circumferentially distributed about the tubular body (20), and in that the tubular body (20) further comprises a plurality of wall sections (44, 46) circumferentially distributed thereabout which join with and extend axially of the main wall means (22), the wall sections (44, 46) being circumferentially interdigitated with the fingers (34, 36) and extend further from the main wall means (22) than the fingers (34, 36). An adapter according to claim 1, wherein the tubular body (20) comprises a plastic material, the catch means (34, 36, 38, 40) being integrally formed with the tubular body (20).

Inventors: FRANCHITTO ANTHONY L, RICE PETER C, SHEN JINGMING J, FRANCHITTO, ANTHONY L., RICE, PETER C., SHEN, JINGMING J.
Applicants: SIEMENS AUTOMOTIVE CORP LP, SIEMENS AUTOMOTIVE CORPORATION
Application year: 1994
Main classification: F02M69
IPC codes: F02M69, F02M61